Recent years have witnessed explosive growth of mobile computing and rapid emergence of new wireless technologies. The key to the success of the next generation of mobile communication systems is providing the user with seamless services at any time, in any place, and in any way. To create a seamless experience, one requirement is providing Quality of Service (QoS) in handovers caused by user mobility and the user's or provider's preferences. Traditionally, there are two types of handovers, horizontal handovers and vertical handovers. As used herein, a horizontal handover is defined as a handover between base stations of the same administrative domain that use the same type of wireless network interface. As used herein, a vertical handover is a handover between base stations that are either in different administrative domains or that use different types of wireless network interfaces. A hyper handover is defined more broadly than a vertical handover. A hyper handover includes not only handovers of a terminal between different administrative domains or types of wireless network interfaces, but also handovers between different terminals and different applications.
Internet Protocol (IP) Mobility Support (“Mobile IP”) as described in IETF RFC 2002 is the current standard for supporting mobility in an IP network. Mobile IP defines two entities for providing mobility support: a home agent and a foreign agent. The packets destined for a wireless terminal are intercepted by the home agent, encapsulated, and tunneled to the foreign agent. The foreign agent decapsulates the packets and forwards them directly to the wireless terminal. Mobile IP provides a framework for allowing users of wireless terminals to roam outside of their home networks without disruption.
Mobile IP, however, was not designed for use in wide-area wireless networks, or to manage mobility between adjacent base stations in the same administrative domain (“micro-mobility”). Mobile IP treats all forms of mobility uniformly, so a user moving a short distance, perhaps between two adjacent base stations in the same administrative domain, can experience significant disruptions, such as loss and delay, due to the frequent registration to the remote home agent. Mobile IP produces a new care-of address on every handover from one base station to another. This introduces complexity and delay for the new QoS reservation or path setup. Additionally, mobile IP provides no support for QoS.
Protocols such as Cellular IP, Hawaii and others have been created for micro-mobility. These protocols try to limit the global updates caused by local movement by either introducing hierarchical foreign agents or smart foreign agents, depending on the network topology. All of these protocols, however, assume a homogeneous network and a common administrative domain. These protocols target horizontal handover problems. For a vertical handover, these protocols usually will not work, because there is usually no one common agent above two separate administrative domains.
There are several frameworks that support QoS, such as integrated service (“Inte-Serv”), differentiated services (“Diff-Serv”), and multi-protocol label switching (“MPLS”). The focus here is on the Inte-Serv framework, which gives the best QoS guarantee once a reservation is built up.
Resource reservation protocol (“RSVP”) is the current standard for supporting Inte-Serv in IP networks. It is well understood that in order to provide guaranteed service some kind of reservation or admission control is needed at the edge router no matter what kind of QoS mechanism is used in the core network. RSVP and extensions thereof are used by a host to request a specific QoS from the network for particular application data flows. It is also used by routers to deliver QoS requests to all nodes along the path of the data flows and to establish and maintain the requested services. RSVP works closely with other components in the Inte-Serv framework including flow specification, routing, admission control, policy control and packet scheduling. RSVP supports both unicast and multicast data flows. RSVP is a receiver-initiated reservation protocol to facilitate the accommodation of heterogeneous receivers and multicast group membership changes. RSVP provides different reservation styles to improve the usage of the bandwidth and allow the multiplexing of different senders in the same multicast group. RSVP uses “soft states” in intermediate routers that automatically expire after some time interval to deal gracefully with route changes or failures.
RSVP does not account for mobility in its receiver-initiating algorithm. Therefore, other protocols that are extensions of the RSVP protocol were created to support mobility, such as Mobile RSVP (MRSVP). These protocols are based on proactively setting up a resource reservation in other base stations where the application is likely to travel. Such proactive reservations, however, could lead to bandwidth waste and large numbers of control messages to refresh the RSVP soft states.
Another extension supports RSVP over an IP-IP tunnel. In Mobile IP without route optimization, communication between a wireless terminal and a corresponding terminal is through an IP-IP tunnel between a home agent and a foreign agent. Hence, an end-to-end RSVP session between the wireless terminal and the corresponding terminal needs to be mapped and supported by the tunneled RSVP session between the home agent and the foreign agent. When the wireless terminal moves from one foreign agent to another foreign agent, current IP-IP tunnel schemes set up a new tunnel RSVP session between the home agent and the new foreign agent. The old and new tunnel RSVP sessions have no knowledge of each other, which leads to double booking of resources on common routers of the two tunnels.
It would be desirable to provide a QoS method for mobility that minimizes the interruption in QoS at the time of a handover. It would also be desirable to provide a QoS method for mobility that localizes the QoS reestablishment to affected parts of a data flow path in a network, and releases the QoS state in an old data flow path (if any) after a handover. It further would be desirable to provide a QoS method for mobility that does not rely on a proactive reservation, to thereby reduce resource overuse. It would also be desirable to provide a QoS method for mobility that is general enough for use in a hyper handover.